Shear Punch Test Research Articles

Shear behavior of human skull bones

A shear-punch test (SPT) experimental method was developed to address the lack of shear deformation and failure response data for the human skull as a function of local bone microarchitecture. Improved understanding of skull deformation and fracture under varying stress-states helps implement mechanism-based, multi-axial material models for finite element analysis for optimizing protection strategies. Shear-punch coupons (N = 47 specimens) were extracted from right-parietal and frontal bones of three fresh-frozen-thawed human skulls. The specimens were kept as full through-thickness or segmented into the three skull constituent layers: the inner and outer cortical tables and the middle porous diploë. Micro-computed x-ray tomography (μCT) before and after SPT provided the bone volume fraction (BVF) as a function of depth for correlation to shear mechanisms in the punched volumes. Digital image correlation was used to track displacement of the punch above the upper die to minimize compliance error. Five full-thickness specimens were subjected to partial indentation loading to investigate the process of damage development as a function of BVF and depth. It was determined that BVF dominates the shear yield and ultimate strength of human skull bone, but the imposed uniaxial loading rate (0.001 and 0.1 s−1) did not have as strong a contribution (p = 0.181–0.806 > 0.05) for the shear yield and ultimate strength of the skull bone layer specimens. Shear yield and ultimate strength data were highly correlated to power law relationships of BVF (R2 = 0.917–0.949). Full-thickness and partial loaded SPT experiments indicate the diploë primarily dictates the shear strength of the intact structure.

Superplasticity of the fine-grained friction stir processed Mg–3Gd–1Zn sheets

Friction stir processing (FSP) was conducted on the hot-rolled Mg–3Gd–1Zn (GZ31) sheets for 1 and 4 passes to create a fine-grained structure. The superplastic behavior of the upper surface layer in the center of the stirred zone (SZ) was evaluated by the localized shear punch test (SPT) in the temperature range of 673–748 K. Microstructural analysis showed that FSP transformed the coarse-grained structure of the hot-rolled alloy with an average grain size of 49.5 μm to the fine and equiaxed grains of 4.6 and 2.7 μm after 1 and 4 passes, respectively. The maximum strain rate sensitivity (SRS) indices (m-values) of 0.23, 0.31, and 0.48 were achieved for the hot-rolled, 1 pass, and 4 passes FSPed conditions at 698 K, respectively. The corresponding activation energies were found to be 321, 212, and 119 kJ mol−1 for these conditions. The shear stress-strain rate behavior of the alloy after 4 FSP passes conformed to regions I, II and III, which is characteristic of superplastic behavior. This was manifested by the high m-value of 0.48 and the activation energy of 119 kJ mol−1, which are indicative of superplastic behavior, caused by the grain boundary sliding (GBS) of the fine equiaxed grains having a large fraction of high angle grain boundaries (HAGBs) of about 87%.

Microstructure and mechanical properties of spark plasma sintered AlCoFeMnNi high entropy alloy (HEA)-carbon nanotube (CNT) nanocomposite

This paper investigates the concept and the possibility of synthesizing high entropy alloy (HEA)/carbon nanotube (CNT) nanocomposites. AlCoFeMnNi was chosen as the matrix and 1 wt% CNT was added as the reinforcement. HEAs have recently gained a lot of attentions as new class of alloys with unprecedented properties, such as superior high temperature corrosion/oxidation resistance, excellent high temperature strength, and perfect structural stability, making HEAs an emerging class of alloys for many demanding applications. AlCoFeMnNi/CNT nanocomposites in this study were produced by combination of mechanical alloying and spark plasma sintering. The microstructure and mechanical properties of produced HEA/CNT nanocomposites were evaluated, using electron microscopy, shear punch, and hardness tests. Results showed that mechanical alloying up to 40 h is enough to transform initial elemental powder mixture to HEA solid solution. Results also showed that CNT addition to the HEA matrix significantly enhances the maximum shear strength of the alloy. Implications of CNT additions to the HEA matrix for the mechanical properties and microstructure HEA/CNT nanocomposite samples were discussed in this paper.

Correlation between shear punch and tensile measurements for an AZ31 Mg alloy processed by equal-channel angular pressing

An AZ31 magnesium alloy was extruded and then processed by equal-channel angular pressing (ECAP) at 200 °C for 1, 2 and 4 passes. The grain structure was refined from 20.2 to 1.6 ?m after 4 passes. The shear punch testing (SPT) technique and uniaxial tensile tests were employed to evaluate the mechanical properties of the extruded and ECAP samples. The 4 pass ECAP alloy showed lower yield stress and higher ductility compared to the as-extruded condition, indicating that texture softening overcame the strengthening effects of grain refinement. The same trends in strength and ductility were also observed in shear punch testing. Three different linear correlations between the shear data and tensile data were established for ductility, yield stress, and ultimate strength. It is shown that SPT is a useful method for evaluating the mechanical properties of small quantities of fine-grained materials processed by ECAP

Derivation of Material Properties Using Small Punch and Shear Punch Test Methods

Derivation of Material Properties Using Small Punch and Shear Punch Test Methods

Superplastic behavior of a severely deformed Mg–6Gd−3Y−0.5Ag alloy

An extruded Mg–6Gd−3Y−0.5Ag magnesium alloy was processed by the simple shear extrusion (SSE) technique at 553 K for 1, 2, 4 and 6 passes to refine the microstructure. The electron back scattered diffraction (EBSD) analysis was used to investigate the microstructural evolutions of the alloy after the SSE processing. The grain orientation spread (GOS) maps revealed that by increasing the SSE passes, the fraction of the fine dynamically recrystallized (DRXed) grains increased accordingly from 3% after 1 pass of SSE to about 81% after 6 passes. The fraction of low angle grain boundaries (LAGBs) was relatively high in the early stages of the SSE processing, due to occurrence of dynamic recovery (DRV), but it began to drop significantly after 4 and 6 SSE passes, as the DRX proceeded. Therefore, continuous dynamic recrystallization (CDRX) was identified as the governing recrystallization mechanism during SSE at 553 K. The shear punch testing (SPT) was carried out at different temperatures and under various shear strain rates to assess the superplastic behavior of the alloys. It was found that only the alloy processed by 6 SSE passes exhibited superplastic flow, for which a maximum strain rate sensitivity (SRS) index of 0.45 and an average activation energy of 112 kJ mol−1 were obtained. Accordingly, grain boundary sliding (GBS) associated with the diffusion of grain boundaries was suggested to be the prevalent deformation mechanism during the superplastic flow of the 6-pass SSEed condition. Moreover, the SPT results revealed that as the SSE pass number increases the maximum SRS indices increase and shift to the lower temperatures indicating the rise in the contribution of the GBS mechanism. The kernel average misorientation (KAM) maps delineated that after SPT at 623 K the fine equi-axed DRXed grains were almost strain-free without any change in their shape for the 6-pass SSEed condition, while the one after 2 SSE passes was comprised of extremely deformed grains along the SPT loading direction.

Finite element analysis of plastic deformation in shear punch test

Strain level and mode of deformation in shear punch testing (SPT) was investigated by finite element method (FEM). The value of equivalent plastic strain was related to the punch displacement (d), punch-die clearance (W), and sample thickness (t) by the relationship of ε∝d/tW. Based on the numerical simulation, it was inferred that the deformation mode depends on the clearance and thickness. It was shown that W/t = 0.1 corresponds to the pure shear mode for AISI 304L austenitic stainless steel, for which the axial components of the plastic strain tend to zero. These findings were found to be consistent with experimental observations and can be utilized in future studies on the mechanical properties and microstructure evolution of materials.

Hot deformation constitutive analysis and processing maps of extruded Mg–Gd binary alloys

Hot shear deformation behavior and optimum processing parameters of the binary Mg–xGd (x = 0.5, 1, and 2 wt%) alloys were studied through the development of constitutive equations and processing maps. Shear punch tests (SPT) were performed in the temperature range of 573–723 K and shear strain rate range of 1.7 × 10−2–1.3 × 10−1 s−1. It was observed that increasing the Gd content retarded the dynamic recrystallization (DRX), leading to smaller DRXed grain size, higher amounts of unDRXed elongated patches, as well as higher shear strength. Based on the stress exponent and deformation activation energy values, calculated through constitutive analysis, the dominant controlling mechanisms were suggested as climb-controlled deformation for the Mg–0.5Gd alloy, and dislocation viscous glide for the Mg–1Gd and Mg–2Gd alloys. The processing maps were plotted to obtain the optimum processing conditions for all tested materials. The results show that the temperature of the safe region with maximum efficiency increased by increasing the amount of Gd addition.

Assessing Microstructure-Local Mechanical Properties in Friction Stir Welded 6082-T6 Aluminum Alloy

The severe deformation and temperature paths in the stir zone, also called weld nugget, of friction stir welded joints result, at very local levels, in significant microstructural variations, such as major differences in grain size or precipitation. One of the most common features of friction stir welds is the presence of successive material layers, known as onion rings; however, little data is available on the mechanical properties of the different regions of the weld nugget, and particularly within the onion ring bands. Such information becomes very important for the integrity of large size friction stir welded structures. In the present study, a comprehensive characterization of onion rings produced during friction stir welding of a 6082-aluminum alloy was carried out. Advanced techniques such as in-situ SEM nanoindentation, EBSD, and high-resolution EDS were used to validate and compare the characteristics of the different bands in the onion rings. The analyses consisted of quantifying variations in grain size, precipitate composition and distribution, crystallographic orientations, and mechanical properties in each band. Furthermore, the tensile strengths of different regions of the weld nugget were evaluated using shear punch testing and correlated with those for the onion ring region in order to determine the impact of the presence of onion rings on weld nugget mechanical properties. The main difference between the alternate bands in the onion ring was found to be due to the difference in their grain size, misorientation, and precipitate content. It was also observed that the bands originate from the base metal and stir zone successively due to the nature of the stirring process, which pulls BM into SZ. Comparison of the shear punch testing results in different regions of the nugget revealed that, in spite of having local differences in the hardness of alternate bands in the onion ring, the presence of onion rings has no significant impact on the deterioration of the mechanical properties of the weld nugget.

Step-by-step texture modification through strain path change toward improvement of the hardening capacity in a twinning-induced-plasticity steel

A novel texture analysis approach is aimed to elucidate the role of strain path change in extending the superior strain hardening capacity of a twinning-induced-plasticity steel up to the large compressive imposed strains at room temperature, in lights of step-by-step texture modification. In this context, activation of different deformation mechanisms during multi-axial forging (MAF) process is fully studied using macrotexture and microtexture analyses by means of calculating Schmid factors of slip and twinning. Synergetic development of deformation twin and dislocation substructure throughout the 1st MAF pass leads to exponential strain hardening rate. This is correlated with the formation of texture components with twin-favoring (near to <001>) and slip-favoring (near to <111> and <110>) orientations in each compression of one MAF pass. Such cooperation can also be reached for larger imposed strains during the 2nd MAF pass at ∑Ԑ = 2.4. However, it results in a steady-state flow behavior through continuous dynamic recrystallization stemming from turning dislocation cells of slip-favoring grains into the new ultrafine grains. This is phenomenal as can be understandable by recognizing the orientation dependency of dislocation substructures including Taylor lattice and dislocation cells as representatives for deformation twins and cross-slip, respectively. Having grains with dislocation cell and Taylor lattice respectively is the origin of facilitating restoration-based process and twinning activation, which modifies the texture by developing a twofold configuration in the course of imposing strain path change. As the second phase of this study, a detailed analyzation of subsequent mechanical responses of MAFed materials is focused through the room-temperature tensile and compression testing methods with the emphasis on the effect of pre-test microtexture on asymmetrical behavior. The shear-punch test is also used to prove the positive effect of recrystallized grains to enhance the mechanical properties.

Hydrostatic cyclic extrusion compression (HCEC) process; a new CEC counterpart for processing long ultrafine-grained metals

Hydrostatic cyclic extrusion–compression as a novel severe plastic deformation method in the processing of the rods is introduced and used for refining ultrafine-grained commercial pure aluminum. HCEC is solving the limitation of the conventional CEC in producing long-length samples by utilizing pressurized hydraulic fluid and eliminating the frictional effects. An increase in the length of the processable sample, a reduction in the processing loads, an intensification in the hydrostatic stress, and improvement in the strain distribution are the novel achievements of the HCEC. The capability of HCEC in grain refinement of the commercial pure aluminum was investigated by transmission electron microscopy analysis. The processed samples showed the grain sizes of 780 nm and 400 nm after the first and second passes of the HCEC, respectively. Furthermore, tensile and shear punch tests were utilized for investigation of the mechanical properties of the unprocessed and HCEC processed rods. An increase in the tensile and shear yield and ultimate strengths after the process confirmed the decreases in grain sizes. The tensile yield and ultimate strengths of the rod after the second cycle of the process reached 170 and 196 MPa, respectively. The same increasing trend as strength was shown in the microhardness after the HCEC. FEM analysis depicted the homogenous distribution of strain along the length of the sample. Also, the independency of the processing force to the length of the sample was shown by the FEM. The implementation of this novel technique looks very interesting for the industrial utilization of SPD techniques, especially in automotive and aerospace industries, which suffer from the limited size of the processing specimens.

Synergistic effect of Nb and Zr additions on the structure-property relationships of nanocrystalline Cu processed by mechanical alloying and hot pressing

In the present study, bulk nanocrystallineCu99.5Zr0.5, Cu99Nb1.0, and Cu98.5Zr0.5Nb1.0alloys have been synthesized by using mechanical alloying followed by hot pressing (HP) at 550 °C. Further, these as-fabricated alloys were annealed at 800 °C and 900 °C for 1 h to investigate the structure-property correlation. Grain size and phase identification has been carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). While mechanical properties were investigated using Vickers hardness and shear punch test (SPT). The grain size of the as-processed alloys was found to remain nanosized 41 ± 2.2 nm in Cu99.5Zr0.5(CZ), 50 ± 1.5 nm in Cu99Nb1.0(CN) and 26 ± 1.2 nm in Cu98.5Zr0.5Nb1.0 (CNZ) even after annealing at 900 °C. This is attributed to the stabilization of the nanosize grains by segregation of solute atoms (Nb and Zr) along grain boundaries and/or Zenner pinning by intermetallic precipitates like Cu5Zr in CZ and CNZ alloys.

Influence of high-pressure torsion on microstructure, hardness and shear strength of AM60 magnesium alloy

The evolution of the microstructure, crystallographic texture and hardness of an AM60 magnesium alloy was studied in the center and the edge parts of disks processed by high-pressure torsion (HPT) technique at room temperature. In addition, the mechanical properties were also tested by shear punch test (SPT). The number of HPT turns varied between ½ and 10. It was found that the grain size of the initial extruded material (~16 μm) decreased to ~2 and ~0.8 μm at the disk center and edge, respectively, even after ½ turn of HPT. Ten turns of HPT resulted in further grain refinement to ~1 and ~0.23 μm at the disk center and edge, respectively. The dislocation density saturated even after ½ turn with the value of ~11 × 1014 m−2. The maximum value of the hardness was ~1300 MPa that was measured at the edge of the disk deformed for ½ turn. Despite the practically unchanged grain size and dislocation density, the hardness decreased between 3 and 10 turns which can be explained by texture softening. A good agreement was observed between the yield strength estimated as one-third of the hardness and the values calculated from the dislocation density, grain size and texture. The difference between the microstructure and hardness obtained for AM60 samples processed by HPT and equal channel angular pressing (ECAP) is discussed.

Effect of Ag Addition on the Hot Deformation, Constitutive Equations and Processing Maps of a Hot Extruded Mg-Gd-Y Alloy

Hot deformation behavior of the extruded Mg-6Gd-3Y (GW63) and Mg-6Gd-3Y-1Ag (GW63-1Ag) alloys was assessed by shear punch testing (SPT) method in the temperature range of 623 K to 723 K and shear strain rate of 1.6 × 10−2 to 1.3 × 10−1 s−1. Microstructural examinations showed that Ag addition decreased the initial grain size from 10.1 to 2.9 µm. According to the hot deformation results, hyperbolic-sine exponents (n-values) of 3.39 and 2.54 were obtained for the Ag-free and Ag-containing alloys, respectively. The corresponding activation energies were found to be 321 and 178 kJ mol−1 for these alloys. Therefore, the controlling deformation mechanisms were defined as viscous glide of dislocation for the Mg-6Gd-3Y alloy and grain boundary sliding for Mg-6Gd-3Y-1Ag. Processing maps were developed based on the dynamic material model (DMM) to determine the flow instability domains during hot deformation. Accordingly, the optimum hot working conditions were found to be in the temperature range of 655 K to 723 K and shear strain rate of 3.3 × 10−2 to 1.3 × 10−1 s−1 for the GW63-1Ag alloy, whereas the safe deformation window for the GW63 alloy was narrowed down to a temperature range of 665 K to 705 K and shear strain rate of 7.2 × 10−2 to 1.3 × 10−1 s−1. The Ag-containing alloy exhibited flow instability regions only at low temperatures and high strain rates. On the other hand, the Ag-free alloy demonstrated other instability domains comprising the formation of mechanical twins and cracking. Electron back-scattered diffraction analysis was utilized to correlate the microstructural evolution of the alloys after shear deformation to the hot working parameters. Continuous dynamic recrystallization was suggested as the main mechanism for generation of the dynamically recrystallized grains during hot deformation of both alloys.

Evolutions of mechanical properties of AISI 304L stainless steel under shear loading

The evolutions of microstructure and mechanical properties during shear punch testing (SPT) of an AISI 304L metastable austenitic stainless steel were studied at deformation temperatures ranging from 0 °C to 550 °C and strain rates in the range of 10-3 s-1 to 1 s-1. Based on the X-ray diffraction (XRD) phase analysis and metallographic observations, it was inferred that by increasing the deformation temperature from 0 °C to 200 °C, the amount of transformed strain-induced martensite decreases at all strain rates, leading to the weakening of the transformation-induced plasticity (TRIP) effect. However, depending on the strain rate, at temperatures higher than 200 °C, an anomalous trend in shear strength was observed, i.e. the shear strength rose by increasing the deformation temperature at low strain rates, due to the dynamic strain aging (DSA) phenomenon. Strain rate sensitivity studies in conjunction with the microstructural evolutions revealed four temperature-dependent regimes: 0–200 °C, 200–300 °C, 300–500 °C and higher than 500 °C, where the respective strain rate sensitivity index (m) becomes positive, zero, negative, and then positive again. These regimes were rationalized based on the TRIP effect, DSA phenomenon, and thermally-activated dislocation glide.

Investigation on Texture Evolution and Recrystallization Aspects of Novel Mg–Zn–Gd–Y–Nd Alloys

Magnesium exhibits substantial property enhancement for a vast range of applications via alloying by rare earth elements (REs). The effect of different amounts of alloying elements (Zn and REs such as Gd, Y and Nd) on the microstructure, texture and mechanical properties of Mg has been investigated here by means of optical microscopy, electron backscattered diffraction, shear punch test and hardness test. Results indicate that the recrystallization process along the grain boundaries consists of dynamic, metadynamic and static recrystallization, while dynamic recrystallization as the dominant mechanism gives rise to bimodal microstructures in as-extruded samples with superior properties. The recrystallized area is narrow at low amounts of alloying elements, whereas addition of higher amounts of alloying elements promotes recrystallization, expands recrystallized areas and weakens texture intensity. Moreover, it is observed that there are some optimal REs ratios promoting a partially recrystallized grain structure which in turn provides higher shear strength, hardness values, and more enhanced ductility as well as a weaker texture. Texture intensity decreases by the increase in the amount of alloying elements

Hot working of SP-700 titanium alloy with lamellar α + β starting structure using a processing map

Abstract In this study, hot deformation behavior of SP-700 titanium alloy was investigated by hot compression tests in the temperature range of 700-9508C and at strain rates of 0.001, 0.1, and 1 s-1. Final mechanical properties of the alloy (hot compressed at different strain rates and temperatures) were investigated using a shear punch testing method at room temperature. The flow curves of the alloy indicated that the yield point phenomenon occurs in the temperature range of 800- 9508C and strain rates of 0.1 and 1 s-1. The microstructural analysis showed that dynamic globularization of the lamellar α phase starts at 7008C and completes at 8008C. The alpha phase was completely eliminated from b matrix due to deformation- induced transformation at 8508C. The microstructure of specimens compressed at 8508C and strain rates of 0.001 and 0.1 s-1showed the serration of beta grain boundaries, whereas partial dynamic recrystallization caused a necklace structure by increasing strain rate up to 1 s-1. The specimen deformed at 7008C and strain rate of 1 s-1was located in the instability region and localized shear bands formed due to the low thermal conductivity of the alloy. The processing map of the alloy exhibited a peak efficiency domain of 54% in the temperature range of 780-8108C and strain rates of 0.001- 0.008 s-1. The hot deformation activation energy of the alloy in the α/β region (305.5 kJ mol-1) was higher than that in the single-phase β region (165.2 kJ mol-1) due to the dynamic globularization of the lamellar a phase.

Evaluating the Mechanical Behavior of ARB Processed Aluminum Composites Using Shear Punch Testing

Multi-layered metal composites have received considerable attention due to their improved mechanical and physical properties. In this study, Al6061/Al2024 composite was processed by accumulative roll bonding (ARB) as a severe plastic deformation technique. Mechanical properties of processed material were evaluated using the uniaxial tensile test and shear punch test method (SPT). The correlation between the results of the tension experiments and shear strengths was calculated. Experimental results demonstrated that the shear strength enhanced with increased number of ARB passes. However, the elongation under shear manifested a reduction when the number of ARB passes increased. Inspection of the results of tensile tests and SPT revealed that they follow a similar trend for both strength and ductility. Therefore, it can be asserted that the shear punch test represents a useful and complementary tool in the mechanical analysis of the ARB sample.

Hot working of SP-700 titanium alloy with lamellar α + β starting structure using a processing map

AbstractIn this study, hot deformation behavior of SP-700 titanium alloy was investigated by hot compression tests in the temperature range of 700-9508C and at strain rates of 0.001, 0.1, and 1 s-1. Final mechanical properties of the alloy (hot compressed at different strain rates and temperatures) were investigated using a shear punch testing method at room temperature. The flow curves of the alloy indicated that the yield point phenomenon occurs in the temperature range of 800- 9508C and strain rates of 0.1 and 1 s-1. The microstructural analysis showed that dynamic globularization of the lamellar α phase starts at 7008C and completes at 8008C. The alpha phase was completely eliminated from b matrix due to deformation- induced transformation at 8508C. The microstructure of specimens compressed at 8508C and strain rates of 0.001 and 0.1 s-1showed the serration of beta grain boundaries, whereas partial dynamic recrystallization caused a necklace structure by increasing strain rate up to 1 s-1. The specimen deformed at 7008C and strain rate of 1 s-1was located in the instability region and localized shear bands formed due to the low thermal conductivity of the alloy. The processing map of the alloy exhibited a peak efficiency domain of 54% in the temperature range of 780-8108C and strain rates of 0.001- 0.008 s-1. The hot deformation activation energy of the alloy in the α/β region (305.5 kJ mol-1) was higher than that in the single-phase β region (165.2 kJ mol-1) due to the dynamic globularization of the lamellar a phase.

Effect of Interlayers on Mechanical Properties of Aluminium Casting over Stainless Steel Pipe for Heat Exchanger Applications

This paper aims to produce Al casting over SS pipe by introducing Cd, Cu, Ag and brass interlayer and to study their effect on the interface bonding between aluminium (Al) and stainless steel (SS). Castings were produced by novel thermocol moulding method and their mechanical properties and metallurgical characteristics were studied. The shear punch test was conducted to evaluate the bond strength of Al–SS bimetallic castings (BmC). Without interlayer, castings showed bond strength of 5.21 MPa, whereas Cd and Cu interlayered BmC showed bond strength of 91.2 MPa and 112.45 MPa, respectively. Ag and brass interlayered BmC showed less effect on bond strength. Interlayers with low melting point and high solubility showed good metallurgical bonding than the interlayers with the high melting point. Eutectic formation of Cd with Al and diffusion of Cu into Al led to the formation of a better metallurgical bond. Hence, they might be used as a potential candidate material for applications like lightweight, hot corrosive fluid and chemical transports.