Quasi-static axial compression behavior of empty and polystyrene foam filled aluminum tubes

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2003Includes bibliographical references (leaves: 82-86)Text in English; Abstract: Turkish and Englishxiv, 86 leavesThe strengthening effect of foam filling and the effect of foam filling on the crushing properties of the light weight foam filled circular tubes were investigated through the polystyrene foam filled thin-walled Al tubes of 16 and 25 mm in diameter. The empty tubes crushed progressively in asymmetric (diamond) mode. The foam filling however turned the deformation mode into progressive axisymmetric (concertina) mode in 25 mm Al tube, while the deformation mode in foam filled 16 mm Al tube remained to be the same with that of the empty tube. The strengthening coefficients of foam-filling defined as the ratio between the increase in the average crushing load of the filled tube with respect to empty tube and plateau load (load corresponding to the plateau stress of the foam) were found to be 1.8 and 3.2 for the concertina and diamond mode of deformation, respectively. The higher value of strengthening in diamond mode of deformation was attributed to the filler deformation beyond the densification region. This was also confirmed by the microscopic observation of the partially crushed sections of the filled tubes. The interaction effect between tube and filler was assessed by the compression testing of the partially foam filled tubes. The effects of filler density, deformation rate (in the range between 0.001-0.04 s-1) and the use of adhesive between the tube wall and filler on the average crushing load, stroke efficiency and specific absorbed energy of the tubes were determined. The specific absorbed energy of the filled tube was compared with that of the empty tubes of wall thickening on the equal mass basis. Finally, two modes of deformation modes were proposed for the crushing behavior of the foam filled thin-walled Al tubes

Optimization of the axial crushing behavior of closed-cell aluminum foam filled welded 1050 al square-cross section crashboxes

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2009Includes bibliographical references (leaves: 194-209)Text in English; abstract: Turkish and Englishxx, 211 leavesThe crushing behavior of partially Al closed-cell foam (Alulight AlSi10) filled 1050H14 Al crash boxes was investigated at quasi-static and dynamic deformation velocities. The quasi-static crushing of empty and filled boxes was further simulated using LS-DYNA. Finally, the crushing of partially foam filled 1050H14 crash boxes was optimized using the response surface methodology. The used optimization methodology was also applied to the boxes made of a stronger Al alloy, 6061T4 Al, and filled with a higher strength Al foam, Hydro Al closed cell foam, in order to clarify the effect of box material and foam filler strength on the crushing behavior of the filled boxes. Within the investigated tube thickness and foam relative density range, the energy absorption of 1050H14 boxes was optimized at 3 mm wall thickness and 0.1114 (Alulight) and 0.0508 (Hydro foam) foam filler relative density. The increase in specific energy absorption of 1050H14 crash box was 5.6% with Alulight and 21.9% for Hydro foam filling. The SEA values of empty, partially and fully foam filled boxes were predicted as function of box wall thickness between 1 and 3 mm and foam filler relative density between 0 and 0.2, using the analytical equations developed for the mean crushing loads. The analysis indicated that both fully and partially foam filled boxes were energetically more efficient than empty boxes above a critical foam filler relative density. Partial foam filling however decreased the critical foam filler density at increasing box wall thicknesses

Predicting energy absorption in a foam-filled thin-walled aluminum tube based on experimentally determined strengthening coefficient

The energy absorption in a foam-filled thin-walled circular Al tube was investigated based on the experimentally determined strengthening coefficient of filling using Al and polystyrene closed-cell foams with three different densities. Foam filling was found to change the deformation mode of tube from diamond (empty tube) into concertina, regardless the foam type and density used. Although foam filling resulted in higher energy absorption than the sum of the energy absorptions of the tube alone and foam alone, it was not effective in increasing the specific energy than simply thickening the tube wall. It was shown that for efficient foam filling an appropriate foam-tube combination must be selected by taking into account the magnitude of strengthening coefficient of foam filling and the foam filler plateau load.TÜBİTAK for the Grant # MISAG-22

Effect of adhesive on the strengthening of aluminum foam-filled circular tubes

Studies of the crushing behavior of closed-cell, aluminum foam-filled aluminum and steel tubes have shown an interaction effect between tubewall and foam filler [1, 2, 3]. The crushing loads of foam-filled tubes are, therefore, found to be higher than the sum of the crushing loads of foam (alone) and tube (alone) mainly due to this effect. Santosa et al. [1], based on FEM results, proposed the following equation for the average crushing load of foam-filled square tubes of length b

SiC-particulate aluminum composite foams produced by powder compacts: Foaming and compression behavior

The foaming behavior of SiC-particulate (8.6% by volume) aluminum composite powder compacts contained Titanium Hydride blowing agent was investigated by heating above the melting temperature (750°C) in a pre-heated furnace. Aluminum powder compacts were also prepared and foamed using similar compaction and foaming parameters in order to determine the effect of SiC-particulate addition on foaming and compression behavior. The linear expansions of the compacts at various furnace holding times were ex situ determined. Optical and scanning electron microscopy techniques were used to characterize prepared and deformed foams microstructures. The SiC-particulate addition was found to increase the linear expansion and reduce the extent of the liquid metal drainage and cell coarsening of the aluminum compacts. The composite foam samples also showed higher compressive stresses, but a more brittle behavior as compared with aluminum foams.TÜBİTAK for the grant #MISAG-13

Quasi-static axial compression behavior of empty and polystyrene foam filled aluminum tubes

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2003Includes bibliographical references (leaves: 82-86)Text in English; Abstract: Turkish and Englishxiv, 86 leavesThe strengthening effect of foam filling and the effect of foam filling on the crushing properties of the light weight foam filled circular tubes were investigated through the polystyrene foam filled thin-walled Al tubes of 16 and 25 mm in diameter. The empty tubes crushed progressively in asymmetric (diamond) mode. The foam filling however turned the deformation mode into progressive axisymmetric (concertina) mode in 25 mm Al tube, while the deformation mode in foam filled 16 mm Al tube remained to be the same with that of the empty tube. The strengthening coefficients of foam-filling defined as the ratio between the increase in the average crushing load of the filled tube with respect to empty tube and plateau load (load corresponding to the plateau stress of the foam) were found to be 1.8 and 3.2 for the concertina and diamond mode of deformation, respectively. The higher value of strengthening in diamond mode of deformation was attributed to the filler deformation beyond the densification region. This was also confirmed by the microscopic observation of the partially crushed sections of the filled tubes. The interaction effect between tube and filler was assessed by the compression testing of the partially foam filled tubes. The effects of filler density, deformation rate (in the range between 0.001-0.04 s-1) and the use of adhesive between the tube wall and filler on the average crushing load, stroke efficiency and specific absorbed energy of the tubes were determined. The specific absorbed energy of the filled tube was compared with that of the empty tubes of wall thickening on the equal mass basis. Finally, two modes of deformation modes were proposed for the crushing behavior of the foam filled thin-walled Al tubes

Compression behavior of extruded polystyrene foams

Mikroskobik ve mekanik test çalışmalarının yardımı ile ekstrude polisitren köpük malzemelerin yapı ve mekanik davranışları belirlenmiştir. Mekanik davranışları üzerindeki anistropi, yoğunluk ve deformasyon hızlarının etkilerini bulmak için polisitren köpükler üç farklı yönde test edilmiştir; bunlar Yükseklik (R), En (W) ve Ekstrüzyon (E) olarak belirlenmiştir. Mikroyapı çalışmaları göstermiştir ki polisitren köpük malzemeler 14 yüzlü (tetrakaidecahedral) kapalı hücrelerden oluşmakta ve bu hücreler R-yönünde uzatılmıştır, diğer iki yönde ise hücre boyutları birbirine çok yakındır. Basma testleri sonucunda en yüksek basma mukavemeti R yönünde olup, tüm yönlerdeki mukavemet değerleri yoğunluk ve basma hızlarının artması ile artmıştır. Deformasyon hızının köpük malzemenin basma davranışı üzerindeki etkisi deformasyon hızı atlama testleri ile kanıtlanmıştır. Son olarak da deformasyon bandı oluşumları ve hücre deformasyonu su içinde ve optik mikroskop altında yapılan basma testleri sonucunda belirlenmiştir.The microstructural and mechanical properties of extruded polystyrene foams were investigated experimentally. In order to determine the effects of anisotropy, foam density and deformation rate on the compression behavior, foams were examined in three different directions, Rise (R), Width (W) and Extrusion (E). Microstructural investigations showed that foam cell structure is the tetrakaidecahedral closed cell and cells are elongated through the R-direction but cell sizes through the W and E directions are very similar. Compression tests revealed that extruded polystyrene foam has higher compression strength in the R-direction. The plateau and collapse stress values increased with increasing of foam density and deformation rate. The effect of deformation rate on the compression behavior of foams was also proved by the stain-rate jump tests. The deformation band formation and cell deformation behavior were determined by in-water and in-situ compression tests, respectivel

The optimisation of the energy absorption of partially Al foam-filled commercial 1050H14 and 6061T4 Al crash boxes

Partially Alulight and Hydro Al closed-cell foam-filled commercial 1050H14 Al and 6061T4 Al crash boxes were optimised using the response surface methodology in order to maximise specific energy absorption (SEA). The quasi-static crushing of empty and filled crash boxes was simulated using LS-DYNA, and the results were further confirmed with experimental quasi-static crushing testing of empty and Alulight foam-filled commercial 1050H14 Al crash boxes. Results showed that partial foam filling of commercial crash boxes increased both SEA and mean load because of foam filler axial and lateral deformation in between the progressing folds of the crash box. Within the studied constraint range of box mean load, box wall thickness and foam filler density, the optimised Alulight and Hydro foam-filled 1050H14 and 6061T4 crash boxes resulted in 26%–40% increase in total energy absorption as compared with empty crash boxes. Considering the same weight basis, the use of a higher yield strength box wall material and higher plateau stresses of Al foam filler resulted in higher energy absorptions in partial foam-filled boxes at relatively low displacements.TÜBİTAK for the grant no. 106M18

Partial Al foam filling of commercial 1050H14 Al crash boxes: The effect of box column thickness and foam relative density on energy absorption

The crushing behavior of partially Al closed-cell foam filled commercial 1050H14 Al crash boxes was determined at quasi-static and dynamic deformation velocities. The quasi-static and dynamic crushing of the boxes were simulated using the LS-DYNA. The results showed that partial foam filling tended to change the deformation mode of empty boxes from a non-sequential to a sequential folding mode. In general, the experimental and simulation results showed similar mean load values and deformation modes. The SEA values of empty, partially and fully foam filled boxes were predicted as function of box wall thickness between 1 and 3 mm and foam filler relative density between 0 and 0.2, using the analytical equations developed for the mean crushing loads. The analysis indicated that both fully and partially foam filled boxes were energetically more efficient than empty boxes above a critical foam filler relative density. Partial foam filling, however, decreases the critical foam filler density at increasing box wall thicknesses.TÜBİTAK for the grant #106M18

Compression behavior of extruded polystyrene foams

Mikroskobik ve mekanik test çalışmalarının yardımı ile ekstrude polisitren köpük malzemelerin yapı ve mekanik davranışları belirlenmiştir. Mekanik davranışları üzerindeki anistropi, yoğunluk ve deformasyon hızlarının etkilerini bulmak için polisitren köpükler üç farklı yönde test edilmiştir; bunlar Yükseklik (R), En (W) ve Ekstrüzyon (E) olarak belirlenmiştir. Mikroyapı çalışmaları göstermiştir ki polisitren köpük malzemeler 14 yüzlü (tetrakaidecahedral) kapalı hücrelerden oluşmakta ve bu hücreler R-yönünde uzatılmıştır, diğer iki yönde ise hücre boyutları birbirine çok yakındır. Basma testleri sonucunda en yüksek basma mukavemeti R yönünde olup, tüm yönlerdeki mukavemet değerleri yoğunluk ve basma hızlarının artması ile artmıştır. Deformasyon hızının köpük malzemenin basma davranışı üzerindeki etkisi deformasyon hızı atlama testleri ile kanıtlanmıştır. Son olarak da deformasyon bandı oluşumları ve hücre deformasyonu su içinde ve optik mikroskop altında yapılan basma testleri sonucunda belirlenmiştir.The microstructural and mechanical properties of extruded polystyrene foams were investigated experimentally. In order to determine the effects of anisotropy, foam density and deformation rate on the compression behavior, foams were examined in three different directions, Rise (R), Width (W) and Extrusion (E). Microstructural investigations showed that foam cell structure is the tetrakaidecahedral closed cell and cells are elongated through the R-direction but cell sizes through the W and E directions are very similar. Compression tests revealed that extruded polystyrene foam has higher compression strength in the R-direction. The plateau and collapse stress values increased with increasing of foam density and deformation rate. The effect of deformation rate on the compression behavior of foams was also proved by the stain-rate jump tests. The deformation band formation and cell deformation behavior were determined by in-water and in-situ compression tests, respectivel