Effect Of Specimen Orientation Research Articles

A virtual stylus method for non-destructive roughness profile measurement of additive manufactured lattice structures

Surface roughness is traditionally evaluated with contact profilometry; however, these methods are not compatible with complex additive manufactured lattice structures due to limited physical access. For these scenarios, computed tomography (CT) is often used to provide qualitative insight into surface roughness but does not directly yield roughness profile data. This research describes a hybrid approach for the non-destructive quantification of roughness profile data for lattice structures based on the mathematical reconstruction and interpretation of CT data. Formal analyses are applied to propose the theoretical minimum CT voxel size required to characterise surface roughness for a specified sampling length. The method is verified against optical data for nominally flat metallic specimens and applied to metallic and polymeric cylinders fabricated by powder bed fusion and material extrusion respectively. This research also assesses the influence of CT reconstruction thresholding as a process variable and finds that roughness profile data is only weakly influenced by thresholding settings, due to scattering effects at the surface — a novel finding that provides certainty for the industrial application of this method. The ability of the proposed method to accurately characterise the inherent surface roughness of these processes as well as the effect of specimen orientation is thus demonstrated, enabling full geometric characterisation supporting subsequent certification analysis. The method can be algorithmically implemented in combination with the generative design of complex lattice structures to support structural certification requirements.

Effects of Specimen Orientation and Heat Treatment on Microstructure and Crack Propagation Path of the IN718 Alloy Built by the Additive Manufacturing Process

Effects of Specimen Orientation and Heat Treatment on Microstructure and Crack Propagation Path of the IN718 Alloy Built by the Additive Manufacturing Process

The anisotropic fatigue properties of extruded Al–Zn–Mg–Cu alloy

The effect of specimen orientation on the fatigue properties of extruded Al–Zn–Mg–Cu alloy was investigated, and the relationship between tensile properties and fatigue strength was established. The results show that the fatigue properties of specimens vary largely with the orientation. The specimens with 0° orientation (relative to extrusion direction) have the highest fatigue strength, i.e. 301.3 MPa, whereas the fatigue strength of specimens with 45°and 90° orientation was reduced by 13.3% and 33.5%, respectively. The fatigue strength is linearly proportional to the elongation. It was found that the crack propagation modes vary with specimen orientation, a result of the grain orientation and intergranular coarse second phase particles, leading to the difference in fatigue lives. In addition, Basquin equations for specimens in the three directions were proposed for fatigue life prediction.

Effect of temperature and specimen orientation on Charpy impact toughness

Steel grade 14MoV6 3 is used for manufacturing of boilers and steam pipelines designed for steam temperatures up to 560°C. This paper presents the experimental analysis which included impact toughness test. The analysis resulted in impact energy values, and their respective components, crack initiation and crack propagation energy, and represents the initial stage of extensive research involving the behavior of 14MoV6 3 steel. The aim was to determine the effects of temperature (room vs. operated), as well as the effects of specimen orientation with regards to the rolling direction, on the impact toughness and the relation between its components.

Effect of Specimen Orientation on the Mechanical Performance of Diffusion Bonded 316 Stainless Steel for Hybrid Printed Circuit Heat Exchangers

Effect of Specimen Orientation on the Mechanical Performance of Diffusion Bonded 316 Stainless Steel for Hybrid Printed Circuit Heat Exchangers

AA5083 (Al\u2013Mg) plates produced by wire-and-arc additive manufacturing: effect of specimen orientation on microstructure and tensile properties

Among various additive manufacturing (AM) technologies, wire-and-arc additive manufacturing (WAAM) is one of the most suitable for the production of large-scale metallic components, also suggesting possible applications in the construction field. Several research activities have been devoted to the WAAM of steels and titanium alloys and, recently, the application of WAAM to aluminum alloys has also been explored. This paper presents the microstructural and mechanical characterization of WAAM plates produced using a commercial ER 5183 aluminum welding wire. The aim is to evaluate the possible anisotropic behavior under tensile stress of planar elements, considering three different extraction directions in relation to the deposition layer: longitudinal (L), transversal (T) and diagonal (D). Compositional, morphological, microstructural and fractographic analyses were carried out to relate the specific microstructural features induced by WAAM to the tensile properties. An anisotropic behavior was found in regard to the specimen orientation, with the lowest strength and ductility found on T specimens. Reasoning to this was found in the presence of microstructural discontinuities unfavorably oriented with regard to the tensile direction. The results of tensile tests also highlighted an overall good mechanical behavior, comparable to that of conventional AA5083-O sheets, suggesting future use in the realization of very complex geometries and optimized shapes for lightweight structural applications.

Brittle fracture manifestation in gas pipeline steels after long-term operation

Gas pipelines are exposed to operational loads combined with corrosive environment action during their long-term service. Complicated service conditions lead to a worsening of steel properties, a reduction of serviceability of the whole object, therefore, a risk of its premature failure rises. Aware of the importance of the existing problem, the aim of this study is the analysis of various mechanical properties of steels after their long-term operation on gas pipelines, and detecting and evaluating fractographic signs of this degradation.Mechanical properties of operated pipe steels characterizing their brittle fracture resistance were significantly decreased. Delamination areas as one of a feature of brittle fracture were identified on the fracture surfaces of specimens after SSRT of the operated steels in corrosive environment. Fracture was initiated from the outer surface of the specimens along the boundaries of ferrite and pearlite grains with significant secondary cracking.The obvious texture in the steels affects noticeably the results of the impact tests. Higher KCV values for the specimens cut in the longitudinal direction relative to the pipe axis comparing with the specimens of transversal orientation were obtained. This was explained by different length of narrow pearlite strips alternated by wide ferrite bands and interrupted by individual ferrite grains depending on the orientation of the specimen fracture surface relative to the pipe axis. Thus, a proper direction of specimen cutting to achieve the maximum sensitivity of KCV parameter to operational degradation of steels is discussed. The effect of specimen orientation on the results of the Charpy testing becomes much more pronounced with steel operation. Defects accumulated in steels during their service are preferentially oriented in the pipe axial direction along the boundaries between ferrite and pearlite strips. Analyzing the fracture surfaces of the Charpy specimens after their impact testing, certain signs of embrittlement were found for long term operated steels in the form of delaminations varying in size and shape, and some cleavage fragments. Furthermore, their percentage of total fracture surface (generally formed by dimples) correlates well with a drop in the impact toughness. The established relationship could be the basis for the introduction of fractographic criteria of the steel serviceability.

Strain-rate dependent occurrence of cleavage fracture in Fe−Si−Al alloys

Iron−silicon steels have excellent magnetic and electrical properties, especially, with increased silicon and aluminum contents. However, increasing alloying with Si and Al reduces the workability of the material, and spontaneous cleavage fracture may occur during production. The main influence factors on the occurrence of cleavage fracture of Fe−Si−Al alloys are investigated in this paper. Fracture mechanics tests are performed at various temperatures and loading rates. The effects of specimen orientation and strain aging are studied. The tests result surprisingly high fracture toughness values. However, cleavage fracture regions are found in the pre-fatigue regions of the specimens, i.e. at much lower loads. In order to resolve this effect, the strain rates during the various fatigue- and fracture experiments are estimated by an analytical model. Additional fatigue experiments are performed at various frequencies where the stress intensity range is increased until cleavage fracture is detected. Similar experiments are conducted at increasing temperatures. The analyses reveal a significant transition behavior of the stress intensity at the onset of cleavage fracture, where the effects of decreasing temperatures and increasing strain rates are equivalent. Measures for avoiding cleavage fracture can be deduced from the results of this investigation.

Effect of specimen orientation on the accuracy of vector field electron tomography.

Vector field electron tomography (VFET) reconstructs vector fields based on phase maps recorded from two or more orthogonal tilt series. The tomographic reconstruction of vector fields involves considerations beyond those involved in the reconstruction of scalar fields. Here we examine the effect of initial magnetization orientation on reconstruction errors. The orientation of a magnetic particle affects the contrast in the phase maps. This, in turn, affects the accuracy of the reconstructed vector fields. We derive expressions that model the dependence of reconstruction errors on initial specimen orientation when using a filtered backprojection algorithm to reconstruct a vector potential from two tilt series. We compare these analytical results with those from numerical simulations. Our results can inform experimental procedures, such as sample preparation techniques and the choice of tilt series orientations. Specimen orientation can be a significant source of error in VFET, and our results can provide the means to minimize these errors.

Creep behaviour of bamboo

The phenomenon of creep, particularly in anisotropic and fibre-reinforced materials, is critical to structural design. The objective of this study is to study the creep behaviour of bamboo in particular considering the effect of specimen orientation. The experiment is motivated by the restriction of sustained load on various materials, particularly fibre reinforced materials, due to creep. In this study, half of the radially-cut Bambusa stenostachya (Tre Gai) specimens subjected to a sustained load were oriented so that the fibre-rich outer culm wall is in tension; the other half were loaded so that the outer culm wall is in compression. All tests were conducted in accordance with, and assessed based on, established creep test standards for wood. The orientation of the specimen was found to have significant effect on both the creep behaviour and residual strength of creep-conditioned specimens. The results showed that the bamboo loaded with the outer culm-wall in tension (OT) exhibited (a) a larger modulus of rupture; (b) a lower apparent modulus of elasticity; and (c) a lower residual strength when compared to specimens with their outer culm-wall in compression (OC). In terms of post-creep residual strength, creep conditioning appeared to have a strengthening effect on OC specimens and a detrimental on OT specimens. Results were assessed against common design values for timber and it concluded that the Tre Gai bamboo is seemingly better able to withstand higher sustained loads than timber.

Acoustic emission study of fatigue crack propagation in extruded AZ31 magnesium alloy

The fatigue crack propagation behavior and corresponding AE characteristics of extruded AZ31 magnesium (Mg) alloy were investigated in this study. The effects of specimen orientation and loading frequency were considered. By combining the AE parameter and waveform analysis with the micro-structural and fractograph observations, the findings of the study showed that crack extension and twinning at the crack tip were two major AE source mechanisms during fatigue crack propagation in the Mg alloy. More twinning events were observed in the transverse direction (TD) specimens than in the extruded direction specimens, which contributed to more cyclic deformation irreversibility and cumulative fatigue damage, leading to worse fatigue performance and higher AE counts in the TD specimens. The results also indicated that increasing the loading frequency could slightly increase the fatigue life, and significantly decrease the AE counts in TD specimens due to the frequency or strain rate dependence of twinning activity. These results suggest that twinning plays an important role in the fatigue process in this Mg alloy, and that the AE technique is capable of detecting crack propagation and twinning events during fatigue.

Tensile properties of the medial patellofemoral ligament: The effect of specimen orientation

For recurrent patellar dislocation, reconstruction of the medial patellofemoral ligament (MPFL) with replacement autografts has often been performed but with only little data on the tensile properties of the MPFL to guide graft selection. With its complex anatomy and geometry, these properties are difficult to obtain. In this study, we showed how the orientation of the femur-MPFL-patella complex (FMPC) during uniaxial tensile testing can have a significant effect on its structural properties. Twenty two FMPCs were isolated from porcine stifle joints and randomly assigned to two groups of 11 each. For the first group, the specimens were loaded to failure with the patella oriented 30 degrees away from the direction of the applied load to mimic its orientation in situ, called natural orientation. In the second group, the patella was aligned in the direction of the tensile load, called non-natural orientation. The stiffness for the natural orientation group was 65±13N/mm, 32% higher than that for the non-natural orientation group (50±17N/mm; p<0.05). The ultimate loads were 438±128N and 386±136N, respectively (p>0.05). Ten out of 11 specimens in the natural orientation group failed at the femoral attachment (the narrowest portion of the MPFL) compared to 6 out of 11 in the non-natural orientation group. Our findings suggest that the specimen orientation that mimics the in-situ loading conditions of the MPFL should be used to obtain more representative data for the structural properties of the FMPC.

The Effect of Specimen Orientation and Thickness on the Initiation of Delamination Crack in X80 Pipeline Steel

The effect of weak interfacial orientation, thickness and the main crack depth on the initiation of delamination crack and main crack in three-point bending specimens of X80 pipeline steel are investigated, using 3D finite element method. Considering the different fracture mechanism of delamination crack and main crack, two different criteria are adopted for them in the simulation. The results reveal that, when the delamination cracks initiates, the initiating position is fixed and the Jz integral of the main crack is a constant for specific weak interfacial orientation specimens with different main crack depth and a certain thickness. When specific weak interfacial orientation specimens have different thickness and a certain main crack depth, the initiating position of delamination crack is equal to the above mentioned, but the Jz integral of the main crack has a ripad decline with the increasing of thickness and then tend to stable. In particular, the delamination crack will not appear for specimens with thin thickness. The thicker the specimen is, the higher the ultimate weak interface strength is needed to prevent the initiation of the delamination crack for specimen with a certain main crack depth. The larger delamination crack will generate, when the specimens have a lower ultimate weak interface strength, a smaller Jz integral of main crack and a larger thickness.

Fatigue performance of injection‐molded short e‐glass fiber reinforced polyamide‐6,6. II. Effects of melt temperature and hold pressure

AbstractTensile and fatigue properties of an injection molded short E‐glass fiber reinforced polyamide‐6,6 have been studied as a function of two key injection molding parameters, namely melt temperature and hold pressure. It was observed that tensile and fatigue strengths of specimens normal to the flow direction were lower than that in the flow direction, indicating inherent anisotropy caused by injection molding. Tensile and fatigue strengths of specimens with weld line were significantly lower than that without weld lines. For specimens in the flow direction, normal to the flow direction and with weld line, tensile strength and fatigue strength increased with increasing melt temperature as well as increasing hold pressure. The effect of specimen orientation on the tensile and fatigue strengths is explained in terms of the difference in fiber orientation and skin‐core morphology of the specimens. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers.

Effect of specimen orientation and heat treatment on electroless Ni-PTFE-MoS2 composite coatings

In this study, the effects of simultaneous co-deposition of polytetrafluoroethylene (PTFE) and MoS2 particles on tribological properties of electroless nickel (EN) coating were studied. The influences of specimen orientation and heat treatment on EN-PTFE-MoS2 composite coatings were also investigated. Scanning electron microscopy was used to study the morphology of coatings and the distributions of the lubricant particles in the deposits. Chemical analyses of coatings were done by electron dispersive spectrometry. The phases of the coatings were identified by X-ray diffraction utilizing CuKα radiation. Wear and friction properties of the coatings were also determined by pin-on-disk wear tester. The wear investigations showed that the EN-PTFE-MoS2 composite coating performs better than EN-PTFE and EN-MoS2 coatings in terms of friction coefficient and wear resistance. PTFE and MoS2 contents of the EN-PTFE-MoS2 coating were increased by changing the specimen orientation from vertical to horizontal configuration, which leads to enhancement in tribological properties of the coating. After heat treatment, the wear rate of EN matrix composite coating decreased with corresponding change in phase structure.

Effect of texture on high temperature deformation behavior at high strain rates in a Mg–3Al–1Zn alloy

The effect of specimen orientation, or texture on high temperature deformation behavior at a high strain rate of 10 3 s −1 was investigated in an extruded Mg–3Al–1Zn alloy rod with 〈 1 0 1 ¯ 0 〉 fiber texture. Uniaxial compression test data were obtained along two specimen directions (longitudinal and transverse directions). The temperature dependence of yield stress was small up to 673 K for both directions, indicating that a diffusion process is not rate-controlling at such a high strain rate. The alloy exhibited strong plastic anisotropy at 10 3 s −1 from room temperature to 673 K. For the transverse specimens, the yield stress was lower than that for the longitudinal specimens. In addition, plastic deformation occurred preferentially in the radial direction of the extruded rod. These results suggest that basal slip is the dominant deformation mechanism for the transverse specimens. On the other hand, strong temperature insensitivity of flow stress as well as concave flow curves observed in the longitudinal specimens suggested the prevalence of twinning.

Effect of specimen orientation and extrusion welds on the fatigue life of an AA6063 alloy

The effect of specimen orientation and extrusion seam welds on the fatigue life of specimens milled from a hollow AA6063 aluminum alloy extrusion profile have been characterized in the form of S–N curves. The fatigue behavior of the fully recrystallized AA6063 alloy reported here is compared to previously reported results on a partially recrystallized AA6082 extruded aluminum alloy [Nanninga N, White C, Furu T, Anderson O, Dickson R. Effect of orientation and extrusion welds on the fatigue life of an Al–Mg–Si–Mn alloy. Int J Fatigue 2008; 30(9): 1569–78]. Specimen orientation with respect to the extrusion direction has a large effect on fatigue life, and is attributed to the orientation of extrusion die lines. Transverse specimens exhibit only a fraction of the high cycle fatigue life exhibited by longitudinal specimens. The presence of seam and/or charge welds, oriented both longitudinal and transverse to the loading direction, may also reduce the fatigue life. However, the effects of these welds are not as significant as the effects of orientation alone, and appear to be related to increased surface roughness at the welds. Variations in fatigue life are explained by surface roughness and variations in microstructure. Grain boundary separation was the primary mechanism of fatigue crack initiation in this study. Results from Auger energy spectroscopy and transmission electron microscope analyses suggest that localized strain in precipitate free zones may assist in this behavior.

Effect of orientation and extrusion welds on the fatigue life of an Al–Mg–Si–Mn alloy

The effect of specimen orientation and extrusion weld (seam and charge) on the fatigue life of specimens from a hollow AA6082 alloy extrusion profile have been characterized in the form of S–N curves. Specimen orientation with respect to the extrusion direction has a large effect on fatigue life. Transverse specimens exhibit only a fraction of the high cycle fatigue life exhibited by longitudinal specimens. The presence of seam and/or charge welds oriented both longitudinally and transverse to the loading direction, also reduces the fatigue life. The effects of these welds, however, are not as significant as the effects of orientation alone. The variations in fatigue life are explained by surface roughness and variations in microstructure.

Facesheet delamination of composite sandwich materials at cryogenic temperatures

A new, novel test method, associated analysis, and experimental procedures are developed to investigate the toughness of the facesheet-to-core interface of a sandwich material at cryogenic temperatures. The test method is designed to simulate the failure mode associated with facesheet debonding due to high levels of gas pressure in the honeycomb core. The effects of specimen orientation are considered, and the results of toughness measurements are presented. Comparisons are made between room and cryogenic test temperatures. It was determined that the test method is insensitive to specimen facesheet orientation and strain energy release rate increases with a decrease in the test temperature. A reasonable agreement between test and simulation was achieved at both temperatures.

Fatigue performance of an injection‐molded short E‐glass fiber‐reinforced polyamide 6,6. I. Effects of orientation, holes, and weld line

AbstractThis article presents the experimental results of stress‐controlled fatigue tests of an injection‐molded 33 wt% short E‐glass fiber‐reinforced polyamide 6,6. The effects of specimen orientation with respect to the flow direction, hole stress concentration, and weld line on the fatigue life have been considered. In addition, the effect of cyclic frequency has been examined. In addition to the modulus and tensile strength, the fatigue strength of the material was significantly higher in the flow direction than normal to the flow direction, indicating inherent anisotropy of the material caused by flow‐induced orientation of fibers. The presence of weld line reduced the modulus, tensile strength, failure strain, and fatigue strength. The fatigue strength of specimens with a hole was lower than that of un‐notched specimens, but was insensitive to the hole diameter. At cyclic frequencies ≤ 2 Hz, failure was due to fatigue, and fatigue life increased with frequency. However, at cyclic frequencies &gt; 2 Hz, the failure mode was a mixture of fatigue and thermal failures, and fatigue life decreased with increasing frequency. POLYM. COMPOS., 27:230–237, 2006. © 2006 Society of Plastics Engineers.